The whole premise - that double negatives don't work for humans - is invalid. Natural languages have and continue to make use of double negatives and double positives (and in some cases, the positive-negative).
Obviously if your specific language doesn't make use of it, or makes use of it in a different way to ruby (e.g. is your natural language treating the second negative as a negation of the negative, or an intensifier of it?) then ruby's grammar will seem unnatural. But that's going to be true for anyone who's trying to map their natural language onto a programming language whose grammar is different to theirs.
Obviously if your specific language doesn't make use of it, or makes use of it in a different way to ruby (e.g. is your natural language treating the second negative as a negation of the negative, or an intensifier of it?) then ruby's grammar will seem unnatural. But that's going to be true for anyone who's trying to map their natural language onto a programming language whose grammar is different to theirs.